This work presents three kinetic models based on a lumping approach to describe the microwave pyrolysis of kraft lignin. The first model considered the formation of the main pyrolysis products, condensable gas, non-condensable gas, and remaining solid, taking into consideration each as an individual lump. The second model investigated the liquid product while dividing the condensable gas into oil and water products. The oil product contains only chemicals, whereas the water product does not contain any chemicals. In the third model, the oil product was separated into four main groups: (1) phenolics, which contain all of the identified phenolic components using a gas chromatography mass spectrometry (GC MS) analyzer, (2) heavy-molecular-weight components, which contain all of the identified heavy-molecular-weight and undefined components, using GC MS, (3) non-phenolic aromatics with a single ring, and (4) aliphatics. The comparison of the predicted results using the estimated kinetic parameters to the experimental data showed the high capability of the presented models to estimate the product yield under the selected conditions.